The present invention relates to semiconductor packages.
A semiconductor device such as a semiconductor switch (e.g. a power MOSFET) is usually packaged and then the package is integrated into an electronic circuit. A conventional package includes a plurality of leads constituting a lead frame, a semiconductor device having the electrodes thereof coupled electrically to the leads for external connection and a molded plastic housing encapsulating at least the semiconductor device and portions of the leads.
Semiconductor devices, and particularly power semiconductor devices, generate heat during operation. The heat so generated must be extracted and dissipated, otherwise the operation of the semiconductor device may be adversely affected. Conventional packages offer less than ideal heat dissipation characteristics.
Furthermore, for economic reasons it is desirable to simplify the configuration and the process for the fabrication of semiconductor packages in order to reduce the cost thereof. Conventional package fabrication may require several costly steps, particularly, in the fabrication of the lead frame, which contribute to the cost of manufacturing.
A package according to the present invention allows for improved heat extraction and dissipation, and also includes features which render the fabrication thereof simpler and less costly.
A semiconductor package according to the present invention includes a plurality of leads each having a bond pad, said leads being embedded partially in a ceramic body, a semiconductor device having a plurality electrodes disposed over the ceramic body, each electrode being electrically coupled to a respective bond pad, and a housing encapsulating at least the semiconductor device.
According to one aspect of the present invention, the ceramic body is made from a thermally conductive ceramic with a high dielectric constant such as aluminum nitride in order to improve the thermal characteristics of the package and electrical isolation.
According to another aspect of the present invention, the semiconductor device is attached to the ceramic body by an adhesive, such as epoxy or solder, and is positioned centrally relative to all the bond pads. That is, the bond pads are redistributed to surround the semiconductor device whereby the distance between the electrodes of the device and the pads may be optimally shortened.
To further enhance the thermal performance of the package the housing may be formed from a moldable ceramic. Fins may be added to the housing to improve thermal convection.
According to another aspect of the present invention the leads (including the bond pads) may have the same thickness, whereby the cost of fabrication of the package may be reduced.
According to another aspect of the present invention, at least one of the bond pads may include a chamfered corner to reduce stress and failure due to fatigue.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.